Multiferroic BaTiO_3-CoFe_2O_4 Nanostructures

摘要

We report on the coupling between ferroelectric and magnetic order parameters in a nanostructured BaTiO_3-CoFe_2O_4 ferroelectromagnet. This facilitates the interconversion of energies stored in electric and magnetic fields and plays an important role in many devices, including transducers, field sensors, etc. Such nanostructures were deposited on single-crystal SrTiO_3 (001) substrates by pulsed laser deposition from a single Ba-Ti-Co-Fe-oxide target. The films are epitaxial in-plane as well as out-of-plane with self-assembled hexagonal arrays of CoFe_2O_4 nanopillars embedded in a BaTiO_3 matrix. The CoFe_2O_4 nanopillars have uniform size and average spacing of 20 to 30 nanometers. Temperature-dependent magnetic measurements illustrate the coupling between the two order parameters, which is manifested as a change in magnetization at the ferroelectric Curie temperature. Thermodynamic analyses show that the mag-netoelectric coupling in such a nanostructure can be understood on the basis of the strong elastic interactions between the two phases.